Present television receivers, such as NTSC (National Television Standards Committee) television receivers, include video processing circuitry that typically must process a video signal conforming to only a single, predetermined video format. Future digital television (DTV) receivers are expected to be implemented substantially in accordance with the transmission standards established by the Advanced Television Standards Committee (ATSC). A similar standard is the European Digital Video Broadcasting (DVB) standard. A compressed digital video system is described in the ATSC digital television standard document A/53, incorporated herein by reference. Moreover, the Moving Pictures Experts Group (MPEG) has promulgated several standards relating to digital data delivery systems. The first, known as MPEG-1, refers to ISO/IEC standards 11172 and is incorporated herein by reference. The second, known as MPEG-2, refers to ISO/IEC standards 13818 and is incorporated herein by reference.
The new DTV standards allow broadcasters to deliver virtually any format up to 1920xc3x971080 pixels. Specifically, DTV receivers must be capable of receiving source video comprising image sequences that vary in spatial resolution (480 lines, 720 lines, or 1080 lines), in temporal resolution (60 fps, 30 fps, or 24 fps), and in scanning format (2:1 interlaced or progressive scan). In addition, it is desirable to convert the format of the received video signal to a preferred format (i.e., a xe2x80x9cnativexe2x80x9d format) of a display device used in conjunction with the receiver.
In one prior art approach, the format of the received television signal is subjected to electronic scan conversion (interpolation, filtering and/or decimation) to adapt the format of the television signal to a xe2x80x9cnative display formatxe2x80x9d of the display device utilized in the particular DTV receiver. Prior art arrangements utilizing this approach first decode the received television signal and decompress the video information within that signal to provide a video information stream. The video information stream is then subjected to, e.g., vertical and/or horizontal interpolation or filtering or decimation to adapt the format of the video signal to the native format of the display device. In addition, it is known to use a frame rate conversion process to adapt the frame rate (i.e., 24 Hz, 30 Hz, 60 Hz) to the frame rate native to the display processing circuitry.
The above described prior art technique for adapting multiple format television signals to a particular native display format disadvantageously utilizes the same computational resources regardless of the format of the received television signal, or the native format of the display device. Thus, even in the case of adapting a low resolution format television signal to a low resolution native display format, the computational resources used by the video decoder are the same as would be used to adapt a high resolution format television signal to a medium, low or high resolution native display format display device.
Therefore, it is seen to be desirable to adapt a computational resource utilization of a video decoder (i.e., processing and memory resources) to the type of signal format received and its appropriate decoding to a native display format of a DTV receiver or to a native processing format of a video processing system, such as a video editing system.
The invention comprises a method an apparatus for allocating processing resources in an information stream decoder in response to format indicia included within a compressed information stream. Specifically, the invention comprises an apparatus and method for decoding a video stream having an associated source video format to produce a decoded video stream having the same format or a different format, in which a computational resource is allocated in response to a change in format between the associated video format and the resultant video format.
The invention provides an efficient, multiple format video signal processing system that allocates processing resources in response to the format of a received video or television signal. The invention may be used in reformatting or transcoding video information between, e.g., various storage media, video or television standards and/or formats. The invention is also advantageously employed within a digital television (DTV) system to adapt a received video format to a native display format.
The invention is based in part on the inventor""s observation that the decompression of different picture sizes require different computational resources, particularly in the case of a high resolution native display format, when smaller picture sizes are decoded (using fewer IDCT resources), greater interpolation (computation of more filter taps) is required.
In one embodiment of the invention, a video decoder architecture senses the format of a received television signal and, in response, allocates arithmetic and logic resources between inverse discrete cosine transfer (IDCT operations) and vertical and/or horizontal interpolation and/or decimation operations.
A method according to the invention, and suitable for use in a system for decoding a compressed video stream, comprises the steps of: identifying a source format of the compressed video stream; determining, using the identified source format, a computational resource requirement suitable for processing the compressed video stream to produce a decompressed video stream having an output format; allocating, in response to the determined resource requirement, computational resources for performing at least an inverse discrete cosine transform (IDCT); and processing the compressed video stream to produce the decompressed video stream having the output format.